Recently, liquid crystal display devices using liquid crystal materials are popular in the daily life. As methods of forming liquid crystal display devices, various modes such as TN (Twisted Nematic) mode liquid crystal, STN (Super Twisted Nematic) mode liquid crystal, TSTN (Triple Super Twisted Nematic) mode liquid crystal, etc., are used. In any one of such different modes, to manufacture the liquid crystal display device, a pair of glass substrates with transparent electrodes formed on are bonded, a liquid crystal is injected into the display cells formed between the pair of glass substrates to form a liquid crystal panel, the liquid crystal panel is processed, and the liquid crystal device is manufactured.
Background arts are disclosed in, e.g., Japanese Laid-open Patent Publication No. 2002-287157, Japanese Patent No. 2511341, Japanese Laid-open Patent Publication No. H05-265014, Japanese Laid-open Patent Publication No. H07-318957, and Japanese Laid-open Patent Publication No. H08-201747.
However, in the conventional manufacturing methods, a pair of glass substrates are bonded to each other to be secured by applying a seal agent to one of the glass substrate of the pair of glass substrates, opposing said one glass substrate to the other glass substrate and physically pressurizing both sides.
The method of physically pressing the pair of glass substrates on both sides cannot avoid disuniform pressure in the glass substrates and has a problem that this causes disuniform gaps of the display cells. It is also a problem that when foreign objects, such as particles, etc., are present on the glass substrates, the glass substrates are damaged by the press. As the liquid crystal display device is thinned, the above-described problems are more serious.
When plastic substrates are used in place of glass substrates, the method of physically pressurizing a pair of plastic substrates on both sides has a problem that when foreign objects, such as particles, etc., are present on the plastic substrates, the plastic substrates are deformed by the pressurization. A problem is that, when a liquid crystal is injected, the air in the display cells is expanded to thereby deform the plastic substrates, and bonded parts are released.